The invention concerns a percussion tool, in particular a hammer drill, wherein the percussion effect on the tool is provided by a striking bolt actively connected with a piston for acting on the end of the tool; the piston is guided in a cylinder sleeve arranged coaxially with a rotating drive, wherein a pressure actuating the movement of the piston is generated in front of the piston by a reciprocating motion.
Hammer drills of this type are known (e.g., see Hilti Operating Instructions for Hammer Drill TE12, W 1030 1081 40-s, printed in Liechtenstein, 1981). In the known configurations, an additional piston is guided back and forth in a cylinder sleeve by means of a connecting rod drive, which additional piston creates the impact motion of the piston connected with the striking bolt. The cylinder sleeve is supported in a hollow drive spindle whereby the rotating motion necessary for the drilling is transmitted to the tool. A disadvantage of these configurations is that because of the need to drive both the drive spindle for the drilling tool and the strike piston, two different driving devices are needed. These devices, especially the drive to generate impact motion, requires much space, so that the housing to contain such a layout must be relatively large and heavy. This is true also for designs (e.g., see Offenlegungsschrift DE No. 32 41 528 A1, corresponding to pending U.S. patent application Ser. No. 06/548,764 filed Nov. 4, 1983 by the applicant of record) already proposed, wherein the cylinder sleeve guiding the piston is itself moved back and forth. Here again, an additional drive must be placed into the housing, the arrangement and dimensions whereof necessarily lead to a relatively voluminous structure.
It is an object of the present invention to minimize the above problems by providing solutions permitting a space saving layout of the drive to produce the reciprocating motion in percussion tools such as hammer drills.